Data insertion apparatus and methods for use with compressed audio/video data

ABSTRACT

Methods, apparatus, and articles of manufacture for performing data insertion in compressed audio/video data streams are disclosed. An example method disclosed herein to insert audience measurement data in a compressed media data stream comprises rearranging data in frames of the compressed media data stream to form contiguous sequences of skip bytes at respective locations in the frames of the compressed media data stream, the audience measurement data to be inserted in the compressed media data stream at the locations of the contiguous sequences of skip bytes, the contiguous sequences of skip bytes having respective lengths, and inserting different types of audience measurement data at the locations of the contiguous sequences of skip bytes in two different frames of the compressed media data stream based on the respective lengths of the contiguous sequences of skip bytes in the two different frames of the compressed media data stream.

RELATED APPLICATION

This patent issued from a continuation of U.S. application Ser. No.11/535,269, filed on Sep. 26, 2006, which is a continuation ofInternational Application Number PCT/US2005/011630, filed on Apr. 7,2005, which claims the benefit of U.S. Provisional Patent ApplicationNo. 60/560,150, filed on Apr. 7, 2004, all of which are herebyincorporated herein by reference in their respective entireties.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to the delivery anddistribution of compressed digital audio/video content such as digitalbroadcast systems and, more specifically, to data insertion andwatermarking apparatus and methods for use with compressed audio/videodata.

BACKGROUND

Digital broadcast systems typically transmit one or more high-bandwidthsignals, each of which is typically composed of a stream of data or datapackets having a plurality of video, audio and/or other digital programsor content multiplexed therein. A number of well-known data compressiontechniques (e.g., audio/video content compression techniques),transmission protocols and the like are typically employed to generateand transmit a multi-program data stream or bit stream, which iscommonly referred to as a transport stream. In particular, digitaltelevision programming is typically transmitted according to a standardpromulgated by the Advanced Television Standards Committee (ATSC). TheATSC standard is a comprehensive standard relating to the conveyance ofdigital television signals. Under the ATSC standard, video informationassociated with a program is encoded and compressed according to thewell-known Moving Pictures Expert Group-2 (MPEG-2) standard and audioinformation associated with the program is encoded and compressedaccording to the well-known AC-3 standard. As a result, an ATSC datastream or bit stream contains video information in the form of MPEG-2packets and audio information in the form of AC-3 packets. However,other digital transmission protocols, data compression schemes and thelike may be used instead.

Some digital broadcasters enable the identification of digital broadcastprograms (e.g., at home sites, reference sites, etc.) by inserting orembedding digital program identification information and/or other data(e.g., watermark data) in the video and/or audio bit stream. Theinserted or embedded digital data is commonly referred to as audiencemeasurement data or content identification data, which may includesignal identification codes (i.e., digital codes that are uniquelyassociated with respective audio/video content portions or programs),date information, time information, consumer identification information,etc. The insertion of audience measurement data at the distributionsystem headend or broadcast station is commonly referred to as an activeaudio/video content identification process because the system headend orbroadcast station actively modifies (i.e., inserts or embeds data in)the transmitted bit streams or transport streams.

Typically, known active data insertion or embedding techniques insert orembed digital data within each of the video and/or audio signals thatmake up the one or more programs (i.e., video and/or audio programs)being transmitted by the broadcast station before the individual videoand/or audio signals are compressed and multiplexed to form a singlemulti-program bit stream or transport stream. However, because thedigital data are inserted in an uncompressed domain (i.e., within theindividual uncompressed audio/video signals), multiple digital datainsertion or embedding devices (e.g., one for each uncompressed programbit stream) are typically required. This requirement for multipledigital information insertion devices is undesirable because itincreases the complexity and operational costs associated with headendor broadcast stations.

Another difficulty that results from inserting or embedding digital datainto individual uncompressed program signals is that subsequentcompression operations (e.g., compression encoding) may corrupt and/oreliminate some or all of the inserted or embedded data. As is known,signal compression techniques usually provide a substantial reduction inthe quantity of data needed to reproduce a video image and/or an audiosignal, but do so at the expense (i.e., the loss) of at least some dataor information. Thus, if compression operations corrupt the inserteddigital data, the home site and/or a central data processing orcollection facility may not be able to accurately identify audio/videocontent.

As noted above, the digital data inserted or embedded by existingbroadcast systems may include watermark data or information, which istypically inserted or embedded in audio and/or video content datastream. However, many existing watermarking techniques are designed foruse with analog broadcast systems. In particular, existing watermarkingtechniques typically convert analog program data to an uncompresseddigital data stream, insert watermark data in the uncompressed digitaldata stream, and convert the watermarked data stream back into an analogformat prior to transmission. Thus, when used with digital audio and/orvideo systems, existing watermarking techniques may decompress thecompressed digital data stream into time-domain samples, insert thewatermark data into the time-domain samples, and recompress thewatermarked time-domain samples into a watermarked compressed digitaldata stream. However, such decompression/compression cycles may causedegradation in quality of the original audio and/or video content.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example system within which the datainsertion and watermarking apparatus and methods described herein may beused to identify digital audio/video content or programs and to generateverification information and/or viewing behavior information based onthe identified audio/video content or programs.

FIG. 2 is a block diagram of an example known system that may be used bythe digital broadcast station of FIG. 1 to insert audience measurementdata in one or more uncompressed audio/video content or program bitstreams.

FIG. 3 is a block diagram of an example system that may be used withinthe digital broadcast station of FIG. 1 to insert audience measurementdata in a compressed audio/video content or program bit stream.

FIG. 4 is a more detailed block diagram that depicts an example mannerin which the data inserter shown in FIG. 3 may be implemented.

FIG. 5 is a more detailed block diagram depicting an example manner inwhich the data insertion unit of FIG. 4 may be implemented.

FIG. 6 is a block diagram of an example processor-based system thatexecutes software or instructions stored on a machine readable medium toimplement the example data inserter shown in FIG. 3.

FIG. 7 is a flow diagram of an example manner in which the processorsystem shown in FIG. 6 may be configured to perform the functions of theexample data inserter shown in FIG. 3.

FIG. 8 is a more detailed flow diagram of an example manner in which thedata insertion block of FIG. 7 may be implemented.

FIG. 9 is a flow diagram of an example method by which the system shownin FIG. 11 may generate viewing behavior and ratings information usingdata inserted by the example data inserter of FIG. 3.

FIG. 10 is a block diagram of another manner in which a data insertermay be configured to insert audience measurement data in a compressedaudio/video content bit stream.

FIG. 11 is a block diagram representation of an example watermarkembedding system.

FIG. 12 is a block diagram representation of an example uncompresseddigital data stream associated with the example watermark embeddingsystem of FIG. 11.

FIG. 13 is a block diagram representation of an example embedding devicethat may be used to implement the example watermark embedding system ofFIG. 11.

FIG. 14 depicts an example compressed digital data stream associatedwith the example embedding device of FIG. 13.

FIG. 15 depicts an example quantization look-up table that may be usedto implement the example watermark embedding system of FIG. 11.

FIG. 16 depicts another example uncompressed digital data stream thatmay be processed using the example watermark embedding system of FIG.11.

FIG. 17 is depicts an example compressed digital data stream associatedwith the example uncompressed digital data stream of FIG. 17.

FIG. 18 is a flow diagram depicting one manner in which the examplewatermark embedding system of FIG. 11 may be configured to embedwatermarks.

FIG. 19 is a flow diagram depicting one manner in which the modificationprocess of FIG. 18 may be implemented.

FIG. 20 is a flow diagram depicting another manner in which the examplewatermarking system of FIG. 11 may be used with the example datainserter of FIG. 3.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of an example system 100 within which the datainsertion apparatus and methods described in greater detail below may beused to identify broadcast digital audio/video content or programs andto generate viewing behavior and ratings information based on theidentified audio/video content. The system 100 includes a digitalbroadcast station 102 that receives digital video and/or audio contentfrom a plurality of digital content providers 104 and 106. The digitalcontent providers 104 and 106 may provide a variety of audio/videocontent such as, for example, television programs, advertisements, audio(e.g., radio) programs, still image information (e.g., web pages), etc.in known manners to the digital broadcast station 102. The digitalbroadcast station 102 transmits one or more signals containing digitalaudio/video content to a reference site 108 and at least one consumptionsite (e.g., a monitored household) 110 via communication paths or links112 and 114. The communication paths or links 112 and 114 may includeany combination of hardwired or wireless links such as, for example,satellite links, wireless land-based links, cable links, etc. Thesignals conveyed via the links 112 and 114 may contain multi-programdata streams or bit streams, which are often referred to as transportstreams and commonly employed with existing digital televisiontransmission systems.

The reference site 108 and the consumption site 110 receive and processthe digital signals or digital audio/video content provided by thedigital broadcast station 102 using the audio/video contentidentification apparatus and methods described herein. Morespecifically, the reference site 108 includes a plurality of decoders(e.g., set-top boxes or the like) 116, 118 and 120 that demodulate,demultiplex and decode audio, video and/or other data packets receivedfrom the digital broadcast station 102. In one example, each of thedecoders 116, 118 and 120 provides audio and/or video data packetsassociated with a different program, which is currently being broadcast,to a reference site processor 122. In other words, the decoder 116 mayprovide data packets associated with a first program while the decoders118 and 120 provide data packets associated with respective second andthird programs. The reference site processor 122 is configured tocontrol and/or has information indicating to which channel, sub-channel,etc. each of the decoders 116, 118 and 120 is currently tuned.

The reference site processor 122 may include apparatus and methods forextracting the data inserted by the digital broadcast station 102 intothe broadcast audio/video content (e.g., one or more transport streams).In particular, the reference site processor 122 may be configured toextract digital codes and/or other data or information inserted by thedigital broadcast station 102 from known locations within data packetsand/or data frames. The reference site processor 122 may send theextracted codes and/or other digital information to a central processingunit 124 that, in turn, may process the extracted codes and/or otherdigital information to generate, for example, broadcast verificationinformation, program lineup information, or any other desiredinformation relating to the audio/video content broadcast by the station102.

The consumption site 110 could be, for example, a statistically selectedhome or residence, a business location, a mobile device (e.g., aportable computer, cellular phone or personal data assistant, etc.) orany other site or device enabling the consumption of video and/or audiocontent or programs. For purposes of simplifying the discussion, FIG. 1depicts a single system or consumption site 110. However, a plurality ofconsumption sites may be configured in manners similar or identical tothat of the example consumption site 110.

The consumption site 110 includes an output unit 128 such as, forexample, a video display, television, speaker, etc. The consumption site110 also includes a decoder (e.g., a set-top box) 130, which may besimilar or identical to the decoders 116-120. As shown in FIG. 1, thedecoder 130 may be serially interposed between the broadcast signal 114and the output unit 128 and provides audio and/or video signals 134 tothe output unit 128 that are used to present the audio and/or videocontent or program currently selected for consumption. For example, inthe case where the broadcast signal 114 is a digital satellite or cabletelevision transmission, the decoder 130 demodulates extracts videoand/or audio data packets associated with a desired channel and/orprogram. The extracted data packets are processed to form the signal 134that can be presented (e.g., displayed) by the output unit 128. Forexample, in the case where the output unit 128 is a television, thesignal 134 may be a composite video signal, an S-video signal, a red,green, blue (RGB) signal, or any other displayable video signal appliedto the appropriate input connections of the output unit 128.

In addition, the decoder 130 also provides signals 136 containingdigital audio/video content data to the site unit 132. The audio/videocontent data may, for example, be digital audio signals provided usingthe well-known Sony Corporation and Philips Corporation DigitalInterface Format (S/PDIF), or any other desired format that providesdata packets associated with digital broadcasts. In that case, theaudio/video content data is compressed digital audio data associatedwith audio/video content to which the decoder is currently tuned andwhich is being consumed via the output unit 128.

In addition to its signal processing functions, the decoder 130 may alsoperform access control functions such as, for example, determining whatprograms are available for consumption by a user of the system 100 basedon subscription status or subscription information associated with thesystem 100, generating displayable program guide information, etc.

The site unit 132 processes the signals 136 received from the decoder130 to extract the inserted data (e.g., audience measurement data)therefrom. The site unit 132 may then convey the extracted digital data(e.g., audience measurement data) to the central processing unit 124.The central processing unit 124 may process the extracted digital datato determine what audio/video content (e.g., channels and/or programs)was consumed, the times at which the audio/video content was consumed,and/or the identities of those who consumed the audio/video content. Inthis manner, the central processing unit 124 may generate viewingbehavior information or statistics, ratings information or any otherdesired information relating to the consumption of audio/video contentat the consumption site 110 or at one or more other consumption sites(none of which are shown).

While the output unit 128, the decoder 130 and the site unit 132 aredepicted in FIG. 1 as separate blocks, the functions performed by theseblocks may be combined or integrated in any desired manner. For example,in the case where the consumption site 110 is a portable device (e.g., apersonal data assistant having a wireless communication interface), thefunctions performed by the blocks 128, 130 and 132 may be integratedwithin the portable device. Alternatively, the functions performed bythe output unit 128 and the decoder 130 may be integrated within theportable device, which is then periodically or continuouslycommunicatively coupled to the site unit 132 to download its extracteddata to the site unit 132. In that case, the site unit 132 may beimplemented as a base unit in which the portable device is periodicallydisposed to perform download operations.

FIG. 2 is a block diagram of an example known system 200 that may beused by the digital broadcast station 102 of FIG. 1 to insert audiencemeasurement data into one or more uncompressed audio/video content orprogram bit streams. The system includes a plurality of data inserters202, 204 and 206, each of which is configured to insert data intorespective uncompressed audio/video content data streams 208, 210 and212. Each of the streams 208, 210 and 212 contains a single audio/videoprogram, which may be provided by a digital content provider similar oridentical to the digital content providers 104 and 106 shown in FIG. 1and/or which may be provided a local source such as, for example, adigital video recorder, a video cassette recorder, or any other suitabledigital media delivery devices.

The data inserters 202, 204 and 206 may be implemented using known datainsertion devices such as vertical blanking inserters, watermarkingencoders and closed caption encoders. The outputs of the data inserters202, 204 and 206 are coupled to respective encoders 214, 216 and 218.The encoders 214, 216 and 218 are compression encoders that compresseach of the individual audio/video content bit streams (into which datahas been inserted) using a known audio/video compression scheme such asfor example, a compression scheme compliant with the AC-3 and/or MPEGstandards.

The compressed audio/video content bit streams output by the encoders214, 216 and 218 are multiplexed to form a single bit stream ortransport stream by a multiplexer 220. The multiplexer 220 may multiplexthe compressed bit streams received from the encoders 214, 216 and 218using a multiplexing scheme compliant with, for example, the ATSC and/orDigital Video Broadcast (DVB) standards. The multiplexer 220 providesits multi-program bit stream or transport stream to a modulator 222,which modulates the transport stream using known techniques, and atransmitter 224, which uses known techniques to transmit or broadcastthe transport stream via, for example, the communication links 112 and114 shown in FIG. 1.

The system 200 may also includes a Program and System InformationProtocol (PSIP) generator 226, which uses well known techniques togenerate a collection of hierarchically interlinked tables that containinformation relating to the location of channels and programs, programscheduling (e.g., program lineup information), information facilitatingthe construction of program guides, as well as unique identifiers suchas transport stream identifiers (TSIDs), each of which uniquelycorresponds to a broadcaster. The PSIP generator 226 provides the PSIPinformation to the multiplexer 220, which multiplexes the PSIPinformation into the transport stream.

In addition, the system 200 may include a data generator 228, which mayprovide interactive program information to the multiplexer 220, whichmultiplexes the interactive program information into the transportstream. For example, the data generator 228 may generate programinformation that may be used at a consumption site (e.g., theconsumption site 110 shown in FIG. 1) to generate a program grid-guideand/or to provide other user interface functionality at the consumptionsite.

While the known system 200 of FIG. 1 enables audience measurement datato be inserted into individual audio/video program bit streams, theinserted data may be corrupted or lost during the encoding orcompression process performed by each of the encoders 214, 216 and 218.In addition, because the data inserters 202, 204 and 206 insert audiencemeasurement data without reference to the information being generated bythe PSIP generator 226, changes in program lineup (e.g., reassignment ofa program by a station to a different sub-channel, removal of a program,etc.) are not considered during the data insertion process. As a result,the inserted audience measurement data extracted at a consumption sitemay not reflect the programs or audio/video content actually consumed.To address this issue, two sets of metadata would have to be maintainedto generate ratings information. In particular, one set of metadataassociated with the inserted data and another set of metadata generatedby the PSIP device (e.g., station or broadcaster metadata that is usedfor program identification). In addition, a mapping between the two setsof metadata would be required so that ratings information couldultimately be provided in terms the metadata generated by the PSIPdevice. Still further, the system 200 requires a separate data inserterfor each program bit stream and, thus, may become overly complex incases where the broadcast station (e.g., the broadcast station 102 ofFIG. 1) multiplexes a large number of programs to form its transportstream or if a new channel is introduced for transmission.

FIG. 3 is a block diagram of an example system 300 that may be usedwithin the digital broadcast station 102 of FIG. 1 to insert audiencemeasurement data (e.g., ancillary codes, metadata, watermark data, etc.)in a compressed audio/video content bit stream. Many of the functionalblocks shown in the system 300 of FIG. 3 are similar or identical tothose shown and described in connection with FIG. 2. However, the system300 interposes a data inserter 302 between the multiplexer 220 and themodulator 222, thereby eliminating the need for the plurality of datainserters 202, 204 and 206 (FIG. 2). In contrast to the data inserters202, 204 and 206, the data inserter 302 operates in a compressed domain.In particular, the data inserter 302 inserts data (e.g., audiencemeasurement data and/or other data) in a multi-program bit stream ortransport stream that contains compressed audio/video data, PSIPinformation generated by the PSIP generator 226 and/or other data (e.g.,watermark data) generated by the data generator 228. The physicalinterfaces of such a data insertion device may be implemented usingknown interfaces such as DVB ASI and SMPTE 310.

As described in greater detail below, the data inserter 302 operates ona bit stream containing frames of data packets that are formatted usinga predefined compression and transmission protocol. In some embodiments,the data inserter 302 temporally packs, time shifts or rearranges datawithin data frames to expand (i.e., increase the size of) apredetermined data area or location within one or more of the dataframes and inserts audience measurement data within the one or moreexpanded predetermined data areas or locations. The inserted audiencemeasurement data may then be extracted by one or more decoders at one ormore consumption sites and reference sites and used to generateconsumption records, verification information, program lineupinformation, viewing behavior information etc. Further, as described ingreater detail below, the data inserter 302 may alternatively oradditionally be configured to insert or embed watermark data in theaudio and/or video content of some or all of the frames of data packetswithout decompressing the audio and/or video data contained therein.

Because the data inserter 302 operates in a compressed domain (i.e., itoperates on bit streams containing compressed data), the audiencemeasurement data that it inserts cannot be corrupted or lost as a resultof compression operations, as is the case with known systems (e.g., theknown system 200 shown and described in connection with FIG. 2). Inaddition, because the data inserter 302 has access to the informationgenerated by the PSIP generator 226, the data inserter 302 alwaysinserts audience measurement data that is consistent with the programlineup information contained with the PSIP tables provided by the PSIPgenerator 226. In this manner, the system 300 maintains two metadatasystems (i.e., the metadata produced by the PSIP device and the metadataproduced as a result of the data insertion process) that contain thesame information. As a result, the system 300 provides audiencemeasurement data that is more reliable than that provided by the knownsystem 200 of FIG. 2, particularly in cases where the broadcast station102 (FIG. 1) makes frequent changes to its program lineup.

The system 300 may also include a data generator 304 that generatesnon-audience measurement data such as, for example, interactive data(e.g., uniform resource locators (URLs), Internet protocol (IP) data,etc.), private or proprietary data, or any other non-audiencemeasurement data. In one example, the data generator 304 may generatedata using the format shown below.

-   -   Time Code: XX    -   Minor Channel/Major Channel: XX/YY    -   Data: http://xx.xx.xxx

The data generator 304 may be separate from the data inserter 302 asshown in FIG. 3, in which case the data generator 304 may becommunicatively coupled to the data inserter 302 via a communicationlink 306 such as for example, a serial interface, an Ethernet compatiblelink, or any other suitable communication link and using protocols suchas PMCP. Alternatively, the data generator 304 may be integral with thedata inserter 302. The data generator 304 may also be coupled to a userinterface 306, which may include a keyboard, monitor, mouse, etc. thatenable an operator to enter data to be inserted via the data generator304 and the data inserter 302.

Now turning to FIG. 4, a more detailed block diagram depicts an examplemanner in which the data inserter 302 shown in FIG. 3 may beimplemented. The example data inserter 302 includes a demultiplexer 400that receives a multi-program bit stream (e.g., an ATSC compliant datastream) from the multiplexer 220 (FIG. 3). The demultiplexer 400separates the multi-program bit stream into a plurality of bit streams,including bit streams containing compressed data associated withindividual audio/video programs, a bit stream containing PSIPinformation, a bit stream containing data generated by the datagenerator 228, etc.

A program information extractor 402 receives the individual bit streamsoutput by the demultiplexer 400 and extracts program informationtherefrom. In particular, the program information extractor 402 mayextract a transport stream identifier, which uniquely corresponds to thebroadcasting source (e.g., the station 102 of FIG. 1) from which themulti-program bit stream was transmitted, major and minor channelinformation for each of the bit streams corresponding to an audio/videoprogram, date and time values for each of the audio/video program bitstreams, as well as any other desired program information.

The audience measurement data generator 404 uses the extracted programinformation provided by the program information extractor 402 togenerate audience measurement data for each of the audio/video programbit streams contained within the multi-program bit stream received bythe demultiplexer 400. The audience measurement data generator 404 maygenerate audience measurement data using the example syntax set forth inTable 1 below.

TABLE 1 Data Field Length in bits AudienceMeasurementDataID 8PayloadStartIndex 4 LenIndex 4 Payload Variable

The data field AudienceMeasurementDataID contains a unique identifierthat may be used by decoders (e.g., the decoders 116, 118, 120, and 130)to identify audience measurement data and/or the audience measuremententity (e.g., a company) that has inserted the data. Such uniqueidentifiers may be known in advance to facilitate the identificationprocess. The data field PayloadStartIndex holds a value indicating theorder in which audience measurement information is stored in thepayload. One example manner in which the values of PayloadStartIndex maycorrespond to payload data organization is set forth in Table 2 below.

TABLE 2 PayloadStartIndex Payload Data Starts With 0 TransportID [bit15-0] 1 Major channel [bit 15-0] 2 Minor channel [bit 15-0] 3 Time [bit31-16] 4 Time [bit 15-0]

The data field LenIndex holds a value that indicates the length of thedata field Payload. One example manner in which the data field LenIndexmay define the length of the data field Payload in set forth in Table 3below.

TABLE 3 LenIndex Payload Length in Bytes 0 2 1 4 2 6 3 8 4 10 

Using the above example data field semantics set forth in Tables 1through 3, if PayloadStartIndex=3 and LenIndex=3, then the payloadcontains eight bytes in the order set forth in Table 4 below. Thus, theLenIndex data field enables modulation of the length of the insertedaudience measurement data as a function of the number of bytes availablein the inserted data location or placeholder.

TABLE 4 Payload Data No. of Bytes Time [bit 31-16] 2 Time [bit 15-0] 2Transport ID [bit 15-0] 2 Major Channel [bit 15-0] 2

Tables 1 through 4 above are merely one example manner in which theaudience measurement data generator 404 may generate audiencemeasurement data. Other data types and formats may be used to formaudience measurement data for any desired application. For example, theTransport ID may be replaced by a proprietary identifier that is usedby, for example, an audience measurement entity (e.g., a company) toidentify a channel with a particular major/minor channel number.Alternatively, the Transport ID may be replaced with a public contentidentifier such as, for example, an ISCII, AD-ID or V-ISAN, which arewell known content identification schemes. The timestamp or timeinformation could be the Time of Day (TOD) as generated by the real-timeclock, a replication of the NTT which is present in the PSIP, an SMPTEtimestamp, or a Time in Program (TIP).

A data insertion unit 406 inserts the audience measurement data providedby the audience measurement data generator 404 in the individual bitstreams, which correspond to the individual audio/video programsprovided by the demultiplexer 400. More specifically, the data insertionunit 406 packs, reorganizes or rearranges compressed data within thedata frames of each audio/video program bit stream to expand apredetermined portion or data area of one or more data frames withinthose compressed data bit streams. As described in greater detail below,the packing, reorganization or rearrangement of data within frames mayresult in certain data being transmitted in a different order and, thus,at a different time than such data would have been transmitted prior tothe packing or reorganization of the data. Thus, the rearrangement ofdata in this manner can result in temporally shifting data within framesso that data within frames is transmitted in a different order than itwould have been without the rearrangement. Regardless of the manner inwhich data is reorganized, packed, etc., the decoding process (e.g., ata consumption site) will render any audio and/or video data packets in atemporally correct order. In any case, audience measurement datapertaining to each of the audio/video bit streams noted above isinserted into one or more of the expanded predetermined portions or dataareas.

In addition to receiving audience measurement data to insert, the datainsertion unit 406 may also receive other data such as, for example,non-audience measurement data to insert from the data generator 304(FIG. 3). As described above, such non-audience measurement data mayinclude interactive data such, for example URLs, applets, scripts, etc.Example syntax for such non-audience measurement data is set forth belowin Tables 5 and 6.

TABLE 5 Data Field Value/Length Interactive Data Identifier 0xBB H DataLength XX bytes Data Type YY Data ZZ

TABLE 6 Data Type Value Data Type Description 0 URL 1 Scripts 2 Applets

Audio/video bit streams having data inserted therein by the datainsertion unit 406 are provided to the program information modifier 408,which may, if needed, modify the program information associated with oneor more of those bit streams. In some cases, depending on where in thebit stream the data insertion unit 406 inserts the audience measurementdata or other data, the program information associated with the bitstream into which the data has been inserted may have to be updated. Forexample, in the case where the program information includes PSIP and/orPSI table information, it may be necessary to modify the information thePSIP and/or PSI table information to reflect changes to reflect thatprivate data has been inserted in the bit stream.

After being processed by the program information modifier 408, amultiplexer 410 receives the individual bit streams, includingaudio/video bit streams into which audience measurement data and/orother data has been inserted by the data insertion unit 406. Themultiplexer 410 also receives program information, which may have beenmodified via the program information modifier 408. For example, themultiplexer 410 may receive bit streams containing modified PSIPinformation. Still other bit streams may be received by the multiplexer410 such as, for example, a bit stream containing other programs ordata. In any event, the multiplexer 410 multiplexes the plurality of bitstreams that it receives into a single multi-program bit stream ortransport stream that may have substantially the same format (e.g., thatis compliant with the same protocol) as the transport stream received bythe demultiplexer 400. However, the multi-program bit stream ortransport stream output by the multiplexer 410 contains data inserted bythe data insertion unit 406 and may contain program information modifiedby the program information modifier 408.

FIG. 5 is a more detailed block diagram depicting an example manner inwhich the data insertion unit 406 may be implemented. The data insertionunit 406 may include a parser 500 that parses out or extracts aparticular type or types of data packets to be passed to a datareorganizer 502. In one example, where data insertion unit 406 isimplemented within the digital broadcast station 102 of FIG. 1 and wherethe digital broadcast station 102 is configured to transmit ATSCcompliant digital television signals, the parser 500 is configured toextract compressed audio data packets compliant with the AC-3 standard.In that example, the data reorganizer 502 is configured to reorganize orrearrange the compressed audio data packets within AC-3 data frames toreduce the number of or to eliminate skip bytes within the AC-3 dataframes.

As is well known, compressed audio bit streams compliant with the AC-3standard typically include frames having one or more skip bytes, whichare formed during the encoding process to maintain a fixed frame sizefor each AC-3 frame and which typically do not contain any usefulinformation. In addition, AC-3 data frames contain an auxiliary datafield, which may be used to transmit information other than compressedaudio data and/or may be used to fine tune the number of bits containedin a frame. However, in practice, the auxiliary data fields are absentin the stream when the “auxiliary data exists” flag is set to zero. Byeliminating skip bytes that occur at the end of each block of audiowithin an AC-3 frame (there are six blocks of audio within each AC-3frame), data space can be created at the end of the AC-3 frame toaccommodate auxiliary data.

As noted above, the data reorganizer 502 reduces the number of oreliminates skip bytes within AC-3 frames and shifts, rearranges, orreorganizes audio data within the AC-3 frames to occupy the eliminatedskip bytes. The result of the shifting is a packing of the compressedaudio data toward one end of the frames to occupy portions of the framespreviously occupied by skip bytes, which effectively temporally shiftsthe relative times at which the shifted audio data within a frame aretransmitted. Another result of this shifting is an increase in thenumber of bits available for the auxiliary data fields. It should berecognized that the reorganization of data within frames as describedabove does not result in any temporal shifting of the manner in whichaudio data are reconstructed and/or rendered. For example, in the casewhere data within AC-3 frames have been reorganized in the mannerdescribed above (e.g., packed), the audio content associated therewithis reconstructed (e.g., rendered) in a temporally correct manner,regardless of the manner in which the data within frames was reorganizedand transmitted.

An auxiliary data field inserter 504 inserts the audience measurementdata generated by the audience measurement data generator 404 into thenewly expanded auxiliary data fields of the AC-3 frames. The insertedaudience measurement data may be formatted as described above inconnection with Tables 1 through 4 above, or in any other desiredmanner. Alternatively or additionally, non-audience measurement dataprovided by the data generator 304 (FIG. 3) may be inserted in theauxiliary data fields of the AC-3 frames by the auxiliary data fieldinserter 504.

After the audience measurement data and/or other data has been insertedin the newly expanded auxiliary data field of the AC-3 frames, an errorchecking value generator 506 generates new error checking values foreach AC-3 frame. In this example, the error checking value generator 506is configured to re-compute the cyclical redundancy check (CRC) values,which represent within each AC-3 frame. Re-computation of the CRC valuesfor the AC-3 frames is necessary because elimination of skip bytes,shifting compressed audio data and inserting data in the AC-3 frameauxiliary data fields renders the original CRC values meaningless (i.e.,the original CRCs are no longer representative of the data contained inthe frames).

In general, the example data inserter 302 (FIG. 3) and data generator304 (FIG. 3) may be implemented using primarily hardware, primarilysoftware or any desired combination of hardware and software. In thecase of a primarily software-based implementation, a computer system orother processor system that executes machine readable instructions orprograms may be used to implement the apparatus and methods describedherein. The machine readable instructions or programs may be embodied insoftware stored on a tangible medium such as a CD-ROM, a floppy disk, ahard drive, a digital versatile disk (DVD), or a memory.

FIG. 6 is a block diagram of an example processor-based system 600 thatexecutes software or instructions stored on a machine readable medium toimplement the example data inserter 302 (FIG. 3) and/or the example datagenerator 304 (FIG. 3). The example processor-based system 600 includesa processor 602, which may be any suitable microprocessor such as, forexample, a processor from the Intel Pentium® family of microprocessors.The processor 602 is communicatively coupled to a non-volatile memory604 and a volatile memory 606. The non-volatile memory 604 may beimplemented using, for example, electrically erasable programmable readonly memory (EEPROM), read only memory (ROM), etc. The volatile memory606 may be implemented using, for example, static random access memory(SRAM), dynamic random access memory (DRAM), etc. The processor 602 isalso coupled to a mass storage device 608, which may be implementedusing, for example, a disk drive that stores digital information using amagnetic or optical media.

The processor 602 retrieves and executes machine readable instructionsor software programs that are stored on one or more of the memories 604and 606 and/or the mass storage device 608 to perform the functions ofthe data inserter 302 and/or data generator 304 shown in FIG. 3.

The processor 602 is also in communication with an input/output (I/O)unit 610, that enables the system 600 to communicate with, for example,the user interface 308 (FIG. 3). The I/O unit 610 may include circuitryfor performing network communication functions (e.g., Ethernetcommunication functions), phone line communication functions (e.g.,modem functions), peripheral device communication functions (e.g.,universal serial bus communications, parallel port communications, etc.)to enable the system 600 to communicate with one or more input devicessuch as, for example, a mouse, keyboard, etc. and/or one or more outputdevices such as, for example, a video display, a printer, etc.

FIG. 7 is a flow diagram of an example manner in which the processorsystem 600 shown in FIG. 6 may be configured to perform the functions ofthe data inserter 302 shown in FIG. 3. Initially, the multi-program bitstream or transport stream received from the multiplexer 220 (FIG. 3) isdemultiplexed into its constituent bit streams (block 700). Inparticular, the transport stream may be separated into a plurality ofaudio/video program bit streams, a bit stream containing PSIPinformation, as well as other bit streams containing other data and/orprogram information. Program information such as, for example, transportstream identifiers, major and minor channel numbers, date and timevalue, etc. are then extracted from the constituent bit streams (block702). The extracted program information is then used to generateaudience measurement data (block 704), which is subsequently inserted inpredetermined portions or data fields within the audio/video bit streams(block 706). The program information may then be modified, if necessary,(block 708) and the constituent bit streams, some of which have beenmodified via insertion of audience measurement data and/or modificationof program information, are multiplexed to form a single transportstream (block 710).

FIG. 8 is a more detailed flow diagram of an example manner in which thedata insertion block 706 of FIG. 7 may be implemented. In particular,the audio/video bit streams are parsed to extract certain data packetsinto which data will be inserted. In one example, as described above,audio data packets compliant with the AC-3 standard are extracted.Turning in detail to FIG. 8, a data frame (e.g., a frame of AC-3 data)is analyzed to determine the skip byte locations (as well as the numberof skip bytes) within the data frame (block 800). The number of skipbytes within the frame is then compared to a predetermined minimumnumber of skip bytes (block 802). Such a minimum number may be selectedto accommodate certain data overhead needed to convey, for example, datawithin an auxiliary data field. For example, in the case of an AC-3 datastream, conveying data within an auxiliary data field requires thepresence of a 14-bit “auxdata length” field. Thus, to send N bits withinan auxiliary data field requires a number of skip bytes sufficient toprovide at least N+14 bits. As is known, the “auxdata length” field isused to indicate the number of bits of auxdata present within a frame.

In any event, if the number of skip bytes is not greater than theminimum require (i.e., there is not a sufficient number of skip bytes toaccommodate the required bit overhead (e.g., the “auxdata length” field)and a number of bits to be transmitted as auxdata), then control isreturn to a calling process. On the other hand, if the number of skipbytes is determined to be greater than minimum required at block 802,then the data within the frame is rearranged so that all of the skipbytes are shifted to one general location (block 804). For example, allof the skip bytes may be moved or shifted to one end of the data frame.In the case of an AC-3 frame, the skip bytes may be moved adjacent tothe “auxdata exists” bit.

After the frame data has been rearranged or shifted at block 804, thedata to be inserted is inserted in the new skip byte locations (block806). Audience measurement data, as well as other data, may then beinserted in the newly expanded auxiliary data field. After inserting thedata, the “auxdata exists” bit is set (e.g., to a logical 1) and theCRC's for the frame are recomputed and modified as a result of themovement of data within the frame (block 808).

FIG. 9 is a flow diagram of an example method by which the system 100shown in FIG. 1 may generate viewing behavior and ratings informationusing data inserted by the data inserter 302 of FIG. 3. Initially, thedigital broadcast station 102 (FIG. 1) inserts audience measurement datainto its broadcast transport stream using, for example, the datainserter apparatus and methods described herein (block 900). One or moreof the decoders 116, 118 and 120 (FIG. 1) together with the referencesite processor 122 (FIG. 1) extract the audience measurement data fromknown locations within the transmitted bit streams (block 902). Forexample, in the case where the data inserted within the compressed audiobit streams compliant with the AC-3, the known locations may be theauxiliary data fields of the AC-3 frames as described above. Thereference site processor 122 (FIG. 1) uses the extracted audiencemeasurement data to generate a program lineup (block 904). Inparticular, because the reference site 108 (FIG. 1) can use its multipledecoders 116, 118 and 120 to receive and process multiple audio/videobit streams simultaneously, the reference site processor 122 (FIG. 1)can simultaneously detect and identify, using the inserted audiencemeasurement data, a plurality of broadcast programs available forconsumption. The reference site 122 (FIG. 1) may then transmit thegenerated program lineup information to the collection site (block 906),which in this case is the central processing facility 124 (FIG. 1).

At the consumption site 110 (FIG. 1), the site unit 132 is configured toextract the inserted audience measurement data from the signal 136(block 908), which, in one example, is an S/PDIF signal containingcompressed audio data compliant with the AC-3 standard. In that case,the inserted audience measurement data is located in the auxiliary datafields of the AC-3 data frames and the site unit 132 (FIG. 1) isconfigured to identify the auxiliary data fields and to extractinformation therefrom. The site unit 132 (FIG. 1) is also coupled to apeople meter and/or other devices that enable the site unit 132 (FIG. 1)to generate demographic information (block 910). For example, the siteunit 132 (FIG. 1) may be configured to detect the identities of theperson or persons currently consuming an audio/video program via theoutput unit 128. In any event, the site unit 132 (FIG. 1) transmits theviewing behavior information (i.e., the audience measurement data,demographic information, etc.) to the collection site (block 912) (i.e.,the central processing facility 124 (FIG. 1)).

The collection site or central processing facility 124 (FIG. 1) thencompares the viewing behavior information received from the consumptionsite 110 (FIG. 1) to the program lineup information received from thereference site 108 (FIG. 1) (block 914). By matching the viewingbehavior information to portions of the program lineup information, thecollection site or central processing facility 124 (FIG. 1) maydetermine the time and manner in which audio/video programs wereconsumed at the consumption site 110 (FIG. 1) and/or other consumptionsites (not shown) and by whom those audio/video programs were consumed.The matching information generated at block 914 may then be used by thecentral processing facility 124 (FIG. 1) to generate ratings information(block 916).

In cases where the data generator 304 (FIG. 3) has provided non-audiencemeasurement data (e.g., interactive data) to the data inserter 302 (FIG.3), the decoder 130 (FIG. 3) and/or site unit 132 (FIG. 3) may extractfrom the auxiliary data fields of the AC-3 frames and process thatnon-audience measurement data. For example, the site unit 132 (FIG. 1)may include or be coupled to a web server (not shown) that enablesactivation of URLs and/or other interactive data. In some cases, thenon-audience measurement data may be appropriately transcoded andconveyed via one or more wireless communication links to a portabledevices such as, for example, a cellular phone, personal data assistantand/or a computer.

Although the example data inserter 302 is depicted in FIG. 3 as beingserially interposed between the multiplexer 220 and the modulator 222,other configurations may be used instead to achieve results identical orsimilar to those described above. FIG. 10 is a block diagram of anothermanner in which a data inserter 1000 may be configured to insertaudience measurement data in a compressed audio/video content or programbit stream. As depicted in FIG. 10, the data inserter 1000 iscommunicatively coupled to the PSIP generator 226, one or more of theencoders 208, 210 and 212 and the multiplexer 220. In thisconfiguration, the data inserter 1000 does not require a demultiplexer(e.g., the demultiplexer 400 of FIG. 4) or a multiplexer (e.g. themultiplexer 410 of FIG. 4). Still other configurations are possible. Forexample, the data inserter 1000 may be integrated with the PSIPgenerator 226 and/or one of more of the encoders 208-212.

While the data insertion apparatus and methods described above have beendescribed with reference to specific examples, the apparatus and methodsmay be implemented in different manners to achieve identical or similarresults. More specifically, although example methods and apparatus mayreorganize (e.g., temporally pack) compressed audio data within AC-3compliant data frames to expand the number of bits available for AC-3frame auxiliary data fields, into which data may be inserted, otherinsertion techniques may be used instead. For example, audiencemeasurement data and/or other data may be inserted in privatedescriptors such as, for example, the ATSC private descriptor, theMPEG-2 metadata descriptor and/or the MPEG-2 private descriptor inProgram System Information (PSI) tables (e.g., the program loop that ispresent in a program map table (PMT) section). Alternatively oradditionally, the audience measurement data and/or other data may beinserted in PES packets, Event Information Tables (EITs), A-90 datapackets and/or null or padding packets to achieve identical or similarresults.

As described above, the data inserter 302 of FIG. 3 may be configured toinsert information (e.g., audience measurement data, non-audiencemeasurement data, etc.) into temporally packed frames of compressedaudio data. In particular, the data inserter 302 (FIG. 3) may temporallypack data packets containing audio and/or video content to facilitatethe insertion of audience measurement data and the like into data spacethat would otherwise be used for skip bytes, auxiliary data bytes,and/or other data space not used to convey audio and/or video contentdata. However, as described in greater detail below, the data inserter302 of FIG. 3 may additionally or alternatively be configured to insertor embed watermark information in data packets containing compressedaudio and/or video content information. More specifically, the datainserter 302 of FIG. 3 may be configured to embed watermarks incompressed digital data streams (i.e., without prior decompression ofthe compressed digital data streams), thereby eliminating the need tosubject compressed digital data streams to additionaldecompression/compression cycles, which may significantly degrade thequality of the audio and/or video content data.

Prior to broadcast, for example, the watermarking methods and apparatusdisclosed herein may be used to unpack the modified discrete cosinetransform (MDCT) coefficient sets associated with a compressed digitaldata stream formatted by a digital audio compression technology such asthe AC-3 compression standard. The mantissas of the unpacked MDCTcoefficient sets may be modified to embed watermarks that imperceptiblyaugment the compressed digital data stream. Upon receipt of thecompressed digital data stream, a receiving device (e.g., a set top boxat a media consumption site) may extract the embedded watermarkinformation. The extracted watermark information may be used to identifythe media sources and/or programs (e.g., broadcast stations) associatedwith media currently being consumed (e.g., viewed, listened to, etc.) ata media consumption site. In turn, the source and program identificationinformation may be used in known manners to generate ratings informationand/or any other information that may be used to assess the viewingbehaviors of individual households and/or groups of households.

FIG. 11 depicts an example watermarking system 1100 that may be used toimplement the data inserter 302 of FIG. 3. The watermarking system 1100may be used instead of or in addition to the data insertion apparatusand methods described in connection with FIGS. 4-8 above. Thus, in someembodiments, the data inserter 302 may be configured to insert audiencemeasurement data into non-content carrying data spaces within temporallypacked frames and may also use the watermarking system 1100 to embedwatermark data in the data packets (within the temporally packed frames)carrying compressed audio and/or video content data.

Now turning in detail to FIG. 11, the example watermark embedding system1100 includes an embedding device 1110 and a watermark source 1120. Theembedding device 1110 is configured to insert watermark data 1130 fromthe watermark source 1120 into a compressed digital data stream 1140.The compressed digital data stream 1140 may be the multi-program datastream provided by, for example, the multiplexer 220 (FIG. 3) and, thus,may include data compressed according to audio compression standardssuch as the AC-3 compression standard and/or the MPEG-AAC compressionstandard. The source of the compressed digital data stream 1140 maysample an audio signal at a sampling rate of, for example, 48 kilohertz(kHz) to form audio blocks as described below. With the AC-3 standard,two different block sizes (i.e., short and long blocks) are typicallyused depending on the dynamic characteristics of the audio signal. Forexample, short blocks may be used to minimize pre-echo for transientsegments of the audio signal and long blocks may be used to achieve highcompression gain for non-transient segments of the audio signal. Inaccordance with the AC-3 compression standard, for example, a shortblock contains 256 samples and a long block contains 512 samples. Inaccordance with the MPEG-AAC compression standard as another example,audio blocks may range in size from 128 to 2048 samples.

Typically, audio compression techniques such as those based on the AC-3compression standard use overlapped audio blocks and the ModifiedDiscrete Cosine Transform (MDCT) algorithm to convert an audio signalinto a compressed digital data stream (e.g., the compressed digital datastream 240 of FIG. 2). As is known, audio compression techniquesdecrease the number of bits required to represent an original audiosignal. In accordance with the AC-3 compression standard, for example,the MDCT algorithm generates MDCT coefficient sets based on audioblocks, each of which contains 256 old samples and 256 new samples(i.e., a 512-sample time domain audio block).

In the example of FIG. 12, an uncompressed digital data stream 1200includes a plurality of 256-sample audio blocks 1210, generally shown asA0, A1, A2, A3, A4, and A5. The MDCT algorithm processes the audioblocks 1210 to generate MDCT coefficient sets 1220, generally shown asMA0, MA1, MA2, MA3, MA4, and MA5. In particular, a sequence of512-sample audio blocks may be generated by concatenating samples fromadjacent audio blocks. An MDCT transform may be performed on thesequence of 512-sample audio blocks to generate MDCT coefficient setswith each MDCT coefficient set having 256 MDCT coefficients. Forexample, the MDCT algorithm may process the audio blocks A0 and A1 togenerate the MDCT coefficient set MAO. The audio block A0 provides 256old samples that are concatenated with 256 new samples provided by theaudio block A1 to generate the MDCT coefficient set MAO, which iscomposed of 256 MDCT coefficients. In particular, the audio blocks A0and A1 may be concatenated to generate a 512-sample audio block A01. TheMDCT algorithm transforms the audio block A01 to generate the MDCTcoefficient set MAO. Likewise, the audio blocks A1 and A2 may beprocessed to generate the MDCT coefficient set MA1. In that case, theaudio block A1 provides 256 old samples that are concatenated with 256new samples provided by the audio block A2 to generate a 512-sampleaudio block A12. The MDCT algorithm transforms the audio block A12 togenerate the MDCT coefficient set MA1, which is composed of 256 MDCTcoefficients. As a result, the audio block A1 serves as an overlappingaudio block that is used to generate the MDCT coefficient sets MA0 andMA1. In a similar manner, the MDCT algorithm may process the audioblocks A2 and A3 to generate the MDCT coefficient set MA2, the audioblocks A3 and A4 to generate the MDCT coefficient set MA3, and the audioblocks A4 and A5 to generate the MDCT coefficient set MA4. Accordingly,the audio block A2 serves as an overlapping audio block to generate theMDCT coefficient sets MA1 and MA2, the audio block A3 serves as anoverlapping audio block to generate the MDCT coefficient sets MA2 andMA3, and the audio block A4 serves as an overlapping audio block togenerate the MDCT coefficient sets MA3 and MA4. Together, the MDCTcoefficient sets 1220 form the compressed digital data stream 1140.

As described in detail below, the embedding device 1110 of FIG. 11 mayembed or insert the watermark data 1130 into the compressed digital datastream 1140. The watermark data 1130 may be used, for example, touniquely identify broadcasters and/or programs so that media consumptioninformation (e.g., viewing information) and/or ratings information maybe produced. Thus, the embedding device 1110 produces a watermarkedcompressed digital data stream 1150 for transmission.

FIG. 13 is a block diagram depicting one manner in which the embeddingdevice 1110 of FIG. 11 may be implemented. In the example of FIG. 13,the embedding device 1110 includes an identifying unit 1310, anunpacking unit 1320, a modification unit 1330, and a repacking unit1340. In should be recognized that in implementations where the datainserter 302 (FIG. 3) is configured to both temporally pack orreorganize data within frames of compressed audio and/or video data andinsert audience measurement information in the contiguous data spacescreated thereby as well as insert watermark data in the compressed datapackets containing audio and/or video content, one or more of the blocksshown in FIG. 13 may be integrated with one or more of the blocks shownin FIGS. 4 and 5. For example, the operations of the identifying unit1310 and the demultiplexer 400 (FIG. 4) may be integrated, theoperations of the unpacking unit 1320 and the program informationextractor 402 (FIG. 4) may be integrated, the operations of themodification unit 1330 and the data insertion unit 406 (FIG. 4) may beintegrated, etc.

It should also be noted that while the operation of the embedding device1110 is described below in accordance with the AC-3 compressionstandard, the embedding device 1110 may be implemented to operate withadditional or other compression standards such as, for example, theMPEG-AAC or the MPEG Layer II compression standards. Further, theoperation of the example embedding device 1110 is described inconjunction with FIG. 14. In particular, the identifying unit 1310 isconfigured to identify one or more frames 1410 associated with thecompressed digital data stream 1140, generally shown as Frame A andFrame B. For example, the compressed digital data stream 1140 may be adigital data stream compressed in accordance with the AC-3 standard(hereinafter “AC-3 data stream”). While the AC-3 data stream 1140 mayinclude multiple channels, in the interest of clarity, the followingexample describes the AC-3 data stream 1140 as including only onechannel. In the AC-3 data stream 1140, each of the frames 1410 includesa number of MDCT coefficient sets 1420. In accordance with the AC-3compression standard, for example, each of the frames 1410 includes sixMDCT coefficient sets (i.e., six “audblk”). In particular, Frame Aincludes the MDCT coefficient sets MA1, MA2, MA3, MA4, and MA5 whileFrame B includes the MDCT coefficient sets MB0, MB1, MB2, MB3, MB4, andMB5.

The identifying unit 1310 is also configured to identify headerinformation associated with each of the frames 1410 such as the numberof channels associated with the AC-3 data stream 1140. While the exampleAC-3 data stream 1140 includes only one channel as noted above, anexample compressed digital data stream having multiple channels isdescribed below in conjunction with FIGS. 16 and 17.

The unpacking unit 1320 is configured to unpack the MDCT coefficientsets 1420 to determine compression information such as, for example, theparameters of the original compression process (i.e., the manner inwhich an audio compression technique compressed an audio signal to formthe compressed digital data stream 1140). For example, the unpackingunit 1320 may determine how many bits are used to represent each of theMDCT coefficients within the MDCT coefficient sets 1420. Thus, in thecase where the original audio sample (e.g., the audio blocks 1210 ofFIG. 12) are each represented using sixteen bits, the MDCT coefficientswithin each of the MDCT coefficient sets 1420 may be represented usingless than sixteen bits. More generally, compression parameters may limitchanges to the AC-3 data stream 1140 to ensure that the AC-3 data stream1140 will provide high quality content. Thus, the embedding device 1110embeds or inserts the watermark data 1130 in the AC-3 data stream 1140based on (e.g., in a manner consistent with) the compression informationidentified by the unpacking unit 1320.

As described in detail in the AC-3 compression standard, compressioninformation also includes a mantissa and an exponent associated witheach MDCT coefficient of the MDCT coefficient sets 1420. Specifically,the presence of audio energy E_(k) either at a particular frequency k(e.g., a tone) or spread across a band of frequencies proximate to theparticular frequency k (e.g., a noise) creates a masking effect. Thatis, the human ear is unable to perceive a change in energy ΔE_(k) belowan energy threshold in a spectral region either at a frequency k orspread across the band of frequencies proximate to the frequency k. As aresult, an MCDT coefficient m_(k) associated with the frequency k may bequantized with a step size related to ΔE_(k). For the AC-3 data stream240, each MDCT coefficient of the MDCT coefficient sets 520 is unpackedas a mantissa M_(k) and an exponent X_(k) such that m_(k)=M_(k)·2^(−X)_(k). The number of bits used to represent the mantissa M_(k) of eachMDCT coefficient of the MDCT coefficient sets 520 may be identifiedbased on known quantization look-up tables published in the AC-3compression standard (e.g., the quantization look-up table 1500 of FIG.15). In the example of FIG. 15, the quantization look-up table 1500provides mantissa codes, mantissa bit patterns, and mantissa values forMDCT coefficients represented by a four-bit number. As described indetail below, the mantissa M_(k) may be used to represent a modifiedvalue of an MDCT coefficient in the MDCT coefficient sets 520 afterwatermarks have been inserted into the AC-3 data stream 240.

The modification unit 1330 is configured to perform an inverse transformof each of the MDCT coefficient sets 1420 to generate inversetransformed time-domain audio blocks 1430, generally shown as TA0′,TA3″, TA4′, TA4″, TA5′, TA5″, TB0′, TB0″, TB1′, TB1″, and TB5′ (i.e.,TA0″ through TA3′ and TB2′ through TB4″ are not shown). In particular,the modification unit 1330 generates an old inverse transformedtime-domain audio block (which is represented as a prime block) and anew inverse transformed time-domain audio block (which is represented asa double-prime block) associated with each of the 256-sample compressedtime-domain audio blocks that were concatenated to form the MDCTcoefficient sets 1420 of the AC-3 data stream 1140. For example, themodification unit 1330 performs an inverse transform on the MDCTcoefficient set MA5 to generate TA4″ and TA5′, the MDCT coefficient setMB0 to generate TA5″ and TB0′, and the MDCT coefficient set MB1 togenerate TB0″ and TB1′. In this manner, the modification unit 1330generates the reconstructed time-domain audio blocks 1440 byreconstructing compressed time-domain audio blocks of the AC-3 datastream 1140. To generate the reconstructed time-domain audio blocks1440, the modification unit 1330 may add inverse transformed time-domainaudio blocks based on, for example, the known Princen-Bradley timedomain alias cancellation (TDAC) technique as described in Princen etal., Analysis/Synthesis Filter Bank Design Based on Time Domain AliasingCancellation, Institute of Electrical and Electronics EngineersTransactions, 34 Acousting, Speech and Signal Processing 1153, 1153-1161(1996). For example, the modification unit 1330 may reconstruct thecompressed time-domain audio block TA5 (i.e., TA5R) by adding the primeaudio block TA5′ and the double-prime audio block TA5″ using thePrincen-Bradley TDAC technique. Likewise, the modification unit 1330 mayreconstruct the compressed time-domain audio block TB0 (i.e., TB0R) byadding the prime audio block TB0′ and the double-prime audio block TB0″using the Princen-Bradley TDAC technique. Thus, the compressedtime-domain audio blocks of the AC-3 data stream 1140 are reconstructed(i.e., the reconstructed time-domain audio blocks 1440) without havingto perform a decompression operation so that the watermark data 1130 maybe embedded or inserted into the AC-3 data stream 1140 as describedbelow.

The modification unit 1330 is configured to insert the watermark data1130 into the reconstructed time-domain audio blocks 1440 to generatewatermarked time-domain audio blocks 1450, generally shown as TA0W,TA4W, TA5W, TB0W, TB1W, and TB2W. To insert the watermark data 1130, themodification unit 1330 generates a modifiable time-domain audio block byconcatenating two adjacent reconstructed time-domain audio blocks tocreate a 512-sample audio block. For example, the modification unit 1330may concatenate the reconstructed time-domain audio blocks TA5R and TB0R(i.e., each is a 256-sample audio block) to form a 512-sample audioblock. In this manner, the modification unit 1330 inserts the watermarkdata 1130 into the 512-sample audio block formed by the reconstructedtime-domain audio blocks TA5R and TB0R to generate the watermarkedtime-domain audio blocks TA5W and TB0W. Encoding processes such as thosedescribed in U.S. Pat. Nos. 6,272,176, 6,504,870, and 6,621,881 may beused to insert or embed the watermark data 1130 into the reconstructedtime-domain audio blocks 1140. The disclosures of U.S. Pat. Nos.6,272,176, 6,504,870, and 6,621,881 are hereby incorporated herein intheir entireties.

In the encoding methods and apparatus described in U.S. Pat. Nos.6,272,176, 6,504,870, and 6,621,881, watermarks may be inserted into a512 sample audio block. For example, each 512 sample audio block carriesone bit of embedded or inserted data of the watermark data 1130. A pairof spectral frequency components with indexes f₁ and f₂ may be modifiedto insert the watermark data 1130. To represent a binary “1”, forexample, data bits associated with the watermark data 1130 may be addedso that the power at the first spectral frequency associated with theindex f₁ becomes a spectral power maximum within a frequencyneighborhood (e.g., f₁−2, f₁−1, f₁, f₁+1, and f₁+2). At the same time,the power at the second spectral frequency associated with the index f₂is attenuated by the watermark data 1130 so that the power at the secondspectral frequency associated with the index f₂ becomes a spectral powerminimum within a frequency neighborhood (e.g., f₂−2, f₂−1, f₂, f₂+1, andf₂+2). On the other hand, to represent a binary “0,” the power at thefirst spectral frequency associated with the index f₁ is attenuated tobe a local spectral power minimum while the power at the second spectralfrequency associated with the index f₂ becomes a local spectral powermaximum. The power at the first and second spectral frequenciesassociated with indexes f₁ and f₂ may be varied from audio block toaudio block in a pseudo-random manner to prevent the watermark data 1130from generating an audible tone.

In addition, a sequence of audio blocks containing a unique pattern ofbinary 1s and 0s is embedded within the audio blocks to provide asynchronization marker. The synchronization marker is followed bypseudo-noise (PN) sequences of bit patterns representing the actual dataof the compressed digital data stream 1140. Each five-bit data group isrepresented by a fifteen-bit PN sequence. The amplitude of the watermarkdata 1130 required for each audio block may be controlled bypsycho-acoustic marking models to ensure perceptual inaudibility of thewatermark data 1130. Even if some of the audio blocks are not coded(i.e., not watermarked) due to the masking constraints, watermark datamay still be recovered because of the redundancy created by the PNsequence(s).

Based on the watermarked time-domain audio blocks 1450, the modificationunit 1330 generates watermarked MDCT coefficient sets 1460, generallyshown as MA0W, MA4W, MA5W, MB0W, and MB5W. Following the exampledescribed above, the modification unit 1330 generates the watermarkedMDCT coefficient set MA5W based on the watermarked time-domain audioblocks TA5W and TB0W. Specifically, the modification unit 1330concatenates the watermarked time-domain audio blocks TA5W and TB0W intoa 512-sample audio block and converts the 512-sample audio block intothe watermarked MDCT coefficient set MA5W, which may be used tosubstitute or replace the original MDCT coefficient set MA5.

The difference between the MDCT coefficient sets 1420 and thewatermarked MDCT coefficient sets 1460 represents a change in the AC-3data stream 1140 as a result of embedding or inserting the watermarkdata 1130. As described in conjunction with FIG. 15, for example, themodification unit 1330 may replace the MDCT coefficient set MA5 with itscorresponding watermarked MDCT coefficient set MA5W. In general, theknown quantization look-up tables (e.g., look-up table 1500 of FIG. 15)may be used to determine new mantissa codes associated with MDCTcoefficients of the watermarked MDCT coefficient sets 1460 to replacethe old mantissa codes associated with the MDCT coefficients of the MDCTcoefficient sets 1420. Thus, the new mantissa codes represent the changein the AC-3 data stream 1140 as a result of embedding or inserting thewatermark data 1130.

In particular, the example quantization look-up table 1500 includesmantissa codes, mantissa bit patterns, and mantissa values for afifteen-level quantization of an example mantissa M_(k) in the range of−0.9333 to +0.9333. While the quantization look-up table 1500 providesmantissa information associated with MDCT coefficients that arerepresented using four bits, the AC-3 compression standard providesquantization look-up tables associated with other suitable numbers ofbits per MDCT coefficient. To illustrate one manner in which themodification unit 1330 may modify a particular MDCT coefficient m_(k)with a mantissa code M_(k) contained in the MDCT coefficient set MA5,assume the original mantissa value is −0.2666 (i.e., − 4/15). Using thequantization look-up table 1500, the mantissa bit pattern correspondingto the particular MDCT coefficient m_(k) in the MDCT coefficient set MA5is determined to be 0101 (i.e., mantissa code of 5). The watermarkedMDCT coefficient set MA5W includes a watermarked MDCT coefficient wm_(k)with a mantissa code WM_(k) (i.e., a desired new mantissa code).Further, assume the new mantissa value of the corresponding watermarkedMDCT coefficient wm_(k) of the watermarked MDCT coefficient set MA5W is−0.4300, which lies between the mantissa codes of 3 and 4. In otherwords, embedding the watermark data 1130, in this example, results in adifference of −0.1667 between the original mantissa value of −0.2666 andthe watermarked mantissa value of −0.4300.

To embed or insert the watermark data 1130 in the AC-3 data stream 1140,the modification unit 1330 may substitute the watermarked MDCTcoefficient set MA5W for the MDCT coefficient set MA5 by modifying theMDCT coefficients in the MDCT coefficient set MA5. In this case, eithermantissa code 3 or mantissa code 4 may replace the mantissa code M_(k)of 5 associated with the MDCT coefficient m_(k) (i.e., an MDCTcoefficient in the MDCT coefficient set MA5) because the watermarkedmantissa code WM_(k) associated with the watermarked MDCT coefficientwm_(k) (i.e., an MDCT coefficient in the watermarked MDCT coefficientset MA5W) lies between the mantissa codes of 3 and 4 (i.e., the mantissavalue corresponding to the watermarked MDCT coefficient wm_(k) is−0.4300). The mantissa value corresponding to the mantissa code 3 is−0.5333 (i.e., − 8/15) and the mantissa value corresponding to themantissa code 4 is −0.4 (i.e., − 6/15). In this manner, the modificationunit 1330 selects the mantissa code 4 (i.e., 0100) instead of themantissa code 3 to replace the mantissa code M_(k) of 5 associated withthe MDCT coefficient m_(k) because the mantissa value −0.4 correspondingto the mantissa code 4 is closer to the mantissa value −0.4300corresponding to the watermarked mantissa code WM_(k) associated withthe watermarked MDCT coefficient wm_(k) than the mantissa value −0.5333corresponding to the mantissa code 3. As a result, the new mantissa bitpattern of 0100, which now corresponds to the watermarked mantissa codeWM_(k) of the watermarked MDCT coefficient wm_(k), replaces the originalmantissa bit pattern of 0101, which corresponds to the mantissa codeM_(k) of 5 associated with the MDCT coefficient m_(k). However, if thenew mantissa value is outside the quantization range of mantissa values(i.e., greater than 0.9333 or less than −0.9333), either the positivelimit of 14 or the negative limit of 0 is selected as the new mantissacode. Likewise, each of the MDCT coefficients in the MDCT coefficientset MA5 may be modified by a corresponding watermarked MDCT coefficientin the watermarked coefficient set MA5W in the manner described above.While the mantissa code associated with each MDCT coefficient of an MDCTcoefficient set may be modified as described above, the exponentsassociated with the MDCT coefficients remain constant.

The repacking unit 1340 is configured to repack the watermarked MDCTcoefficient sets 1460 associated with each frame of the AC-3 data stream1140 for transmission. In particular, the repacking unit 1340 identifiesthe position of each MDCT coefficient set within a frame of the AC-3data stream 1140 so that the corresponding watermarked MDCT coefficientset may replace the MDCT coefficient set. To rebuild a watermarkedversion of Frame A, for example, the repacking unit 1340 may identifythe position of the MDCT coefficient sets MA0 to MA5 to substitute thecorresponding watermarked MDCT coefficient sets MA0W to MA5W for theMDCT coefficient sets MA0 to MA5. Using the unpacking, modifying, andrepacking processes described herein, the AC-3 data stream 1140 remainsa compressed digital data stream while the watermark data 1130 isembedded or inserted in the AC-3 data stream 1140. As a result, theembedding device 1110 inserts or embeds the watermark data 230 into theAC-3 data stream 240 without additional decompression/compression cyclesthat may degrade the quality of the content in the AC-3 data stream1140.

While the AC-3 data stream 1140 is described in conjunction with FIG. 14to include a single channel for simplicity, the methods and apparatusdisclosed herein may be applied to compressed digital data streamshaving audio blocks associated with multiple channels such as 5.1channels as described below (i.e., five full-bandwidth channels). In theexample of FIG. 16, an uncompressed digital data stream 1600 may includea plurality of audio block sets 1610. Each of the audio block sets 1610may include audio blocks associated with multiple channels 1620 and 1630including, for example, a front left channel, a front right channel, acenter channel, a surround left channel, a surround right channel, and alow-frequency effect (LFE) channel (e.g., a sub-woofer channel). Forexample, the audio block set AUD0 includes an audio block AOL associatedwith the front left channel, an audio block A0R associated with thefront right channel, an audio block A0C associated with the centerchannel, an audio block A0SL associated with the surround left channel,an audio block A0SR associated with the surround right channel, and anaudio block A0LFE associated with the LFE channel. In another example,the audio block set AUD1 includes an audio block A1L associated with thefront left channel, an audio block A1R associated with the front rightchannel, an audio block A1C associated with the center channel, an audioblock A1SL associated with the surround left channel, an audio blockA1SR associated with the surround right channel, and an audio blockA1LFE associated with the LFE channel.

Each of the audio blocks associated with a particular channel in theaudio block sets 1610 may be processed in a similar manner as describedabove in conjunction with FIGS. 14 and 15. For example, the audio blocksassociated with the center channel 1710 of FIG. 17, generally shown asA0C, A1C, A2C, and A3C, may be compressed to generate the MDCTcoefficient sets 1720 associated with a compressed digital data stream1700. As noted above, each of the MDCT coefficient sets 1720 may bederived from a 512-sample audio block formed by concatenating an old256-sample audio block and a new 256-sample audio block. In particular,the MDCT algorithm may process the audio blocks 1710 (e.g., A0C throughA5C) to generate the MDCT coefficient sets (e.g., M0C through M5C).

Based on the MDCT coefficient sets 1720 of the compressed digital datastream 1700, the identifying unit 1310 identifies a plurality of framesand header information associated with each of the frames as describedabove. The header information includes compression informationassociated with the compressed digital data stream 1700. For each of theframes, the unpacking unit 1320 unpacks the MDCT coefficient sets 1720to determine the compression information associated with the MDCTcoefficient sets 1720. For example, the unpacking unit 1320 may identifythe number of bits used by the original compression process to representthe mantissa of each MDCT coefficient in each of the MDCT coefficientsets 1720. Such compression information may be used to embed thewatermark data 1130 as described above in conjunction with FIG. 15. Themodification unit 1330 then generates inverse transformed audio blocks1730, generally shown as TA0C″, TA1C′, TA1C″, TA2C′, TA2C″, and TA3C′.In particular, the inverse transformed audio blocks 1730 include oldinverse transformed time-domain audio blocks (which are represented asprime blocks) and new inverse transformed time-domain audio blocks(which are represented as double-prime blocks). By adding thecorresponding prime blocks and double-prime blocks based on, forexample, the Princen-Bradley TDAC technique, compressed time-domainaudio blocks of the compressed digital data stream 1700 may bereconstructed (i.e., the reconstructed time-domain audio blocks 1740).For example, the modification unit 1330 may add the inverse transformedaudio blocks TA1C′ and TA1C″ to reconstruct the compressed time-domainaudio block TA1C (i.e., TA1CR). Likewise, the modification unit 1330 mayadd the inverse transformed audio blocks TA2C′ and TA2C″ to reconstructthe compressed time-domain audio block TA2C (i.e., TA2CR). To insert thewatermark data 1130, the modification unit 1330 first concatenates twoadjacent reconstructed time-domain audio blocks to create a 512-sampleaudio block (i.e., a modifiable time-domain audio block). For example,the modification unit 1330 may concatenate the reconstructed time-domainaudio blocks TA1CR and TA2CR, each of which is a 256-sample short blockto form a 512-sample audio block. Accordingly, the modification unit1330 inserts the watermark 1130 into the 512-sample audio block formedby the reconstructed time-domain audio blocks TA1CR and TA2CR togenerate the watermarked time-domain audio blocks TA1CW and TA2CW.

Based on the watermarked time-domain audio blocks 1750, the modificationunit 1330 may generate the watermarked MDCT coefficient sets 1760. Forexample, the modification unit 1330 may concatenate the watermarkedtime-domain audio blocks TA1CW and TA2CW to generate the watermarkedMDCT coefficient set M1CW. Accordingly, the modification unit 1330modifies the MDCT coefficient sets 1720 by replacing each of the MDCTcoefficient sets 1720 with a corresponding one of the watermarked MDCTcoefficient sets 1760. For example, the modification unit 1330 maysubstitute the watermarked MDCT coefficient set M1CW for the originalMDCT coefficient set M1C. In particular, the modification unit 1330 maysubstitute the MDCT coefficients in the watermarked coefficient set M1CWfor the MDCT coefficients in the original MDCT coefficient set M1C. Theembedding device 1140 may repeat the process described above for audioblocks associated with each channel to insert the watermark data 1130into the compressed digital data stream 1700.

FIG. 18 is a flow diagram depicting one manner in which the examplewatermark embedding system of FIG. 11 may be configured to embedwatermarks. Persons of ordinary skill in the art will appreciate thatthe example process of FIG. 18 may be implemented as machine accessibleor readable instructions utilizing any of many different programmingcodes stored on any combination of machine-accessible media such as avolatile or nonvolatile memory or other mass storage device (e.g., afloppy disk, a CD, and a DVD). For example, the machine accessibleinstructions may be embodied in a machine-accessible medium such as aprogrammable gate array, an application specific integrated circuit(ASIC), an erasable programmable read only memory (EPROM), a read onlymemory (ROM), a random access memory (RAM), a magnetic media, an opticalmedia, and/or any other suitable type of medium. The example process ofFIG. 18 may be implemented using, for example, any desired processorsystem such as a system similar or identical to the system 600 of FIG.6. Further, although a particular order of actions is illustrated inFIG. 18, persons of ordinary skill in the art will appreciate that theseactions can be performed in other temporal sequences. Again, the flowdiagram 1800 is merely provided and described in conjunction with thecomponents of FIGS. 11 to 14 as an example of one way to configure asystem to embed watermarks in a compressed digital data stream.

In the example of FIG. 18, the process begins with the identifying unit1310 (FIG. 13) identifying a frame associated with the compresseddigital data stream 1140 (FIG. 11) such as Frame A (FIG. 14) (block1810). The identified frame may include a plurality of MDCT coefficientsets formed by overlapping and concatenating a plurality of audioblocks. In accordance with the AC-3 compression standard, for example, aframe may include six MDCT coefficient sets (i.e., six “audblk”).Further, the identifying unit 1310 (FIG. 13) also identifies headerinformation associated with the frame (block 1820). For example, theidentifying unit 1310 may identify the number of channels associatedwith the compressed digital data stream 1140. The unpacking unit 1320then unpacks the plurality of MDCT coefficient sets to determinecompression information associated with the original compression processused to generate the compressed digital data stream 1140 (block 1830).In particular, the unpacking unit 1320 identifies the mantissa M_(k) andthe exponent X_(k) of each MDCT coefficient m_(k) of each of the MDCTcoefficient sets. The exponents of the MDCT coefficients may then begrouped in a manner compliant with the AC-3 compression standard. Theunpacking unit 1320 (FIG. 13) determines the number of bits used torepresent the mantissas of each of the MDCT coefficients so that asuitable quantization look-up table specified the AC-3 compressionstandard may be used to modify the plurality of MDCT coefficient sets asdescribed above in connection with FIG. 15.

As illustrated in FIG. 19, the modification process 1840 begins by usingthe modifying unit 1330 (FIG. 13) to perform an inverse transform of theMDCT coefficient sets to generate inverse transformed audio blocks(block 1910). In particular, the modification unit 1330 generates an oldinverse transformed time-domain audio block (which is represented as aprime block) and a new inverse transformed time-domain audio block(which is represented as a double-prime block) associated with each ofthe 256-sample compressed time-domain audio blocks of the MDCTcoefficient sets. As described in conjunction with FIG. 14, for example,the modification unit 1330 may generate TA4″ and TA5′ from the MDCTcoefficient set MA5, TA5″ and TB0′ from the MDCT coefficient set MB0,and TB0″ and TB1′ from the MDCT coefficient set MB1. For each compressedtime-domain audio block, the modification unit 1330 adds correspondingprime and double-prime blocks to reconstruct the compressed time-domainaudio block based on, for example, the Princen-Bradley TDAC technique(block 1920). Following the above example, the prime block TA5′ and thedouble-prime block TA5″ may be added to reconstruct the compressedtime-domain audio block TA5 (i.e., the reconstructed time-domain audioblock TA5R) while the prime block TB0′ and the double-prime block TB0″may be added to reconstruct the compressed time-domain audio block TB0(i.e., the reconstructed time-domain audio block TB0R).

To insert the watermark 1130, the modification unit 1330 generatesmodifiable time-domain audio blocks using the reconstructed time-domainaudio blocks (block 1930). The modification unit 1330 may generate a512-sample time-domain audio block using two adjacent reconstructedtime-domain audio blocks. For example, the modification unit 1330 maygenerate a modifiable time-domain audio block by concatenating thereconstructed time-domain audio blocks TA5R and TB0R.

Implementing an encoding process such as, for example, one or more ofthe encoding methods and apparatus described in U.S. Pat. Nos.6,272,176, 6,504,870, and/or 6,621,881, the modification unit 1330inserts the watermark data 1130 into the modifiable time-domain audioblocks (block 1940). For example, the modification unit 1330 may insertthe watermark data 1130 into the 512-sample time-domain audio blockgenerated using the reconstructed time-domain audio blocks TA5R and TB0Rto generate the watermarked time-domain audio blocks TA5W and TB0W.Based on the watermarked time-domain audio blocks and the compressioninformation, the modification unit 1330 generates watermarked MDCTcoefficient sets (block 1950). As noted above, two watermarkedtime-domain audio blocks, where each block includes 256 samples, may beused to generate a watermarked MDCT coefficient set. For example, thewatermarked time-domain audio blocks TA5W and TB0W may be concatenatedto generate the watermarked MDCT coefficient set MA5W.

Based on the compression information associated with the compresseddigital data stream 1140, the modification unit 1330 calculates themantissa value associated with each of the watermarked MDCT coefficientsin the watermarked MDCT coefficient set MA5W as described above inconjunction with FIG. 15. In this manner, the modification unit 1330 canmodify the original MDCT coefficient sets using the watermarked MDCTcoefficient sets to embed or insert the watermark data 1130 in thecompressed digital data stream 1140 (block 1960). Following the aboveexample, the modification unit 1330 may replace the original MDCTcoefficient set MA5 with the watermarked MDCT coefficient set MA5W. Inparticular, the modification unit 1330 may replace an original MDCTcoefficient in the MDCT coefficient set MA5 with a correspondingwatermarked MDCT coefficient in the watermarked MDCT coefficient setMA5W. Alternatively, the modification unit 1330 may compute thedifference between the mantissa codes associated with the original MDCTcoefficient and the corresponding watermarked MDCT coefficient (i.e.,ΔM_(k)=M_(k)−WM_(k)) and modify the original MDCT coefficient based onthe difference ΔM_(k). After modifying the original MDCT coefficientsets, the modification process 1840 terminates and returns control toblock 1850.

Referring back to FIG. 18, the repacking unit 1340 repacks the frame ofthe compressed digital data stream (block 1850). In particular, therepacking unit 1340 identifies the position of the MDCT coefficient setswithin the frame so that the watermarked MDCT coefficient sets mayreplace the MDCT coefficient sets to rebuild the frame. At block 1860,if the embedding device 1130 determines that additional frames of thecompressed digital data stream 1140 need to be processed, then controlreturns to block 1810. Otherwise, if all frames of the compresseddigital data stream 1140 have been processed, then the process 1800 mayterminate.

As noted above, known watermarking techniques typically decompress acompressed digital data stream into uncompressed time-domain samples,insert the watermark into the time-domain samples, and recompress thewatermarked time-domain samples into a watermarked compressed digitaldata stream. In contrast, the digital data stream 1140 remainscompressed during the unpacking, modifying, and repacking processesdescribed herein. Thus, the watermark data 1130 is embedded into thecompressed digital data stream 1140 without having to perform additionaldecompression/compression cycles that may degrade the quality of theaudio and/or video content in the compressed digital data stream 1400.

FIG. 20 is a flow diagram depicting one manner in which the example datainserter 302 (FIG. 3) may be configured to perform the watermarkingoperations described in connection with FIGS. 11-19. However, beforedescribing the operations depicted in FIG. 20 in detail, a briefdescription of the manner in which the example data inserter 302 (FIG.3) maps minor channel number and source identifier information to datalocations within an AC-3 compliant data stream is provided below. Inparticular, the data inserter 302 (FIG. 3) may be configured to store(or have access to) a static or fixed mapping of source identifiers tominor channel numbers. An example of such a mapping is depicted below inTable 7.

TABLE 7 SID Minor Channel Number xx 1 yy 2 zz 3 . . . . . . . . . N

While example mapping depicted in Table 7 above can be used to determinethe source identifier associated with a given minor channel number, theidentifiers used to identify minor channel information within an AC-3data stream are dynamically allocated. As a result, another dynamicmapping must be used to enable the extraction of audio informationassociated with a particular minor channel. To provide such a dynamicmapping, an array PID[k], where k=1 to N for N minor channels, may beused to provide the dynamically allocated AC-3 data stream identifierscorresponding to each of the available minor channels. The array PID[k]may be updated (i.e., kept consistent with current identifierallocation) by parsing allocation information from the PSI and PSIPtables described above. Once the dynamically allocated identifier usedto identify audio information associated with a particular minorchannel, the source identifier (SID) associated with that minor channelmay be determined using, for example, a table such as that shown aboveas Table 7. It should be recognized that the example static and dynamicmappings described above may be more generally applied to audio and/orvideo data streams having formats similar to or different from AC-3compliant data streams.

In the flow diagram in FIG. 20, a watermarking process 2000 embeds orinserts watermark data for a limited amount of time in the data streamsassociated with a sequence of minor channels. The embedding or insertionof watermark data is typically a computationally and, thus, timeintensive process. Thus, to ensure that a finite amount of delay isimparted to a data stream into which watermark data is embedded orinserted, the process 2000 inserts or embeds watermark data in each of aplurality of audio data streams, each of which may be associated with aparticular minor channel, for a limited amount of time. In this mannerthe amount of delay imparted to each of the data streams can to belimited (i.e., made finite) so that any real time decoding and/orrendering process associated with the data stream is not affected in aperceptible manner.

Now turning in detail to the example process 2000 depicted in FIG. 20, aminor channel index k is initialized to one (block 2002). Next, theprogram identifier (PID) associated with a first minor channel number isset equal to the value stored in the dynamic minor channel mapping arrayat the index k (i.e., PID[k] as described above) to filter or extractdata associated with the first minor channel number from an audio (e.g.,AC-3 compliant) data stream (block 2004). The data packets containingaudio content (i.e., payload packets to be transmitted) are then parsedfrom the minor channel data filtered at block 2004 and sent to awatermarking operation (block 2006). The watermarking operation may besimilar or identical to that described above in connection with FIGS.11-19. The remaining non-payload data (e.g., header and otherencapsulating information) is then buffered with placeholders for theremoved audio payload data (block 2008).

The process 2000 then determines if the payload data sent to thewatermarking operation at block 2006 has been watermarked and is nowavailable for transport (block 2010). If the watermarked data is not yetavailable, the process returns control to block 2006. On the other hand,if the watermarked data is available, the process embeds, inserts orpopulates the corresponding buffered non-payload data in the appropriatecorresponding placeholder locations (block 2012). Once the watermarkeddata has been inserted in the data stream of the minor channel currentlybeing watermarked, the watermarked data stream is then sent to be output(i.e., transmitted) (block 2014). The process then checks if the amountof time for which the process 2000 has inserted watermarked data exceedsa predetermined time limit (block 2016). For example, the process mayinsert watermark information into the data streams associated with eachminor channel for a predetermined amount of time (e.g., five seconds).The amount of elapsed insertion time may be determined using, forexample, the number of bits transmitted divided by the transmission bitrate. Alternatively, a timer function within a processor system or thelike may be used to measure a predetermined amount of time. If thepredetermined amount of insertion time has not elapsed at block 2016,the process returns control to block 2006. On the other hand, if thepredetermined amount of time has elapsed at block 2016, then the index kis incremented using a modulo-based counter (block 2018). In particular,the index k is incremented at block 2018 to vary from one to N.

The process then checks if the end of the transport stream has beendetected (block 2020). If the end of the transport stream has not beendetected at block 2020, then the process returns control to block 2004.On the other hand, if the end of the transport stream is detected atblock 2020, then any remaining buffered data is flushed to be output(i.e., transmitted) (block 2022). While the example process 2000depicted in FIG. 20 is configured to watermark each of a sequence ofminor channels for a finite time period (e.g., a periodic round robintechnique for a plurality of minor channels), other architectures and/ortechniques could be used instead. For example, in the event thatadditional delay is acceptable, watermark data may be inserted orembedded into a plurality of minor channel data streams simultaneously(i.e., rather than one at a time in sequence as described in connectionwith FIG. 20).

The methods and apparatus disclosed herein are particularly well suitedfor use with data streams implemented in accordance with the AC-3standard. However, persons of ordinary skill in the art will appreciatethat the teachings of the disclosure may be applied to other digitalaudio and/or video encoding techniques, standards, etc.

In addition, while this disclosure is made with respect to exampletelevision systems, it should be understood that the disclosed system isreadily applicable to many other media systems. Accordingly, while thisdisclosure describes example systems and processes, persons of ordinaryskill in the art will readily appreciate that the disclosed examples arenot the only way to implement such systems.

Although certain methods, apparatus and articles of manufacture havebeen described herein, the scope of coverage of this patent is notlimited thereto. To the contrary, this patent covers all embodimentsincluding apparatus, methods and articles of manufacture fairly fallingwithin the scope of the claims, either literally or under the doctrineof equivalents.

1. A method to insert audience measurement data in a compressed mediadata stream, the method comprising: rearranging data in frames of thecompressed media data stream to form contiguous sequences of skip bytesat respective locations in the frames of the compressed media datastream, the audience measurement data to be inserted in the compressedmedia data stream at the locations of the contiguous sequences of skipbytes, the contiguous sequences of skip bytes having respective lengths;and inserting different types of audience measurement data at thelocations of the contiguous sequences of skip bytes in two differentframes of the compressed media data stream based on the respectivelengths of the contiguous sequences of skip bytes in the two differentframes of the compressed media data stream.
 2. A method as defined inclaim 1 wherein inserting the different types of audience measurementdata comprises: formatting the audience measurement data into payloadsegments corresponding to the different types of audience measurementdata; inserting a first sequence of the payload segments in a firstframe of the compressed media data stream based on a length of a firstcontiguous sequence of skip bytes in the first frame; and inserting asecond sequence of the payload segments in a second frame of thecompressed media data stream based on a length of a second contiguoussequence of skip bytes in the second frame, the length of the secondcontiguous sequence of skip bytes being different from the length of thefirst contiguous sequence of skip bytes.
 3. A method as defined in claim2 wherein the first sequence of the payload segments includes all of thepayload segments, and the second sequence of the payload segmentsincludes a subset of the payload segments.
 4. A method as defined inclaim 2 wherein the second sequence of the payload segments has adifferent order and a different number of payload segments than thefirst sequence of the payload segments.
 5. A method as defined in claim1 further comprising: formatting the audience measurement data into aplurality of payload segments containing the different types of audiencemeasurement data, the plurality of payload segments including atransport identifier segment, a major channel segment, a minor channelsegment and a time segment, the audience measurement data furtherincluding a first index to represent an ordering of the payload segmentsand a second index to represent a number of payload segments to beincluded in a particular frame of the compressed media data stream;varying the ordering of the payload segments inserted at the locationsof the contiguous sequences of skip bytes in the two different frames ofthe compressed media data stream; and varying the number of the payloadsegments inserted at the locations of the contiguous sequences of skipbytes in the two different frames of the compressed media data streambased on the respective lengths of the contiguous sequences of skipbytes in the two different frames of the compressed media data stream.6. A method as defined in claim 1 further comprising extracting programand system information protocol data multiplexed with the compressedmedia data stream to determine the audience measurement data.
 7. Amethod as defined in claim 1 further comprising modifying program andsystem information protocol data multiplexed with the compressed mediadata stream based on the audience measurement data inserted in thecompressed media data stream.
 8. A tangible article of manufacturestoring machine readable instructions which, when executed, cause amachine to at least: rearrange data in frames of a compressed media datastream to form contiguous sequences of skip bytes at respectivelocations in the frames of the compressed media data stream, whereinaudience measurement data is to be inserted in the compressed media datastream at the locations of the contiguous sequences of skip bytes, thecontiguous sequences of skip bytes having respective lengths; and insertdifferent types of audience measurement data at the locations of thecontiguous sequences of skip bytes in two different frames of thecompressed media data stream based on the respective lengths of thecontiguous sequences of skip bytes in the two different frames of thecompressed media data stream.
 9. A tangible article of manufacture asdefined in claim 8 wherein the machine readable instructions, whenexecuted, further cause the machine to: format the audience measurementdata into payload segments corresponding to the different types ofaudience measurement data; insert a first sequence of the payloadsegments in a first frame of the compressed media data stream based on alength of a first contiguous sequence of skip bytes in the first frame;and insert a second sequence of the payload segments in a second frameof the compressed media data stream based on a length of a secondcontiguous sequence of skip bytes in the second frame, the length of thesecond contiguous sequence of skip bytes being different from the lengthof the first contiguous sequence of skip bytes.
 10. A tangible articleof manufacture as defined in claim 9 wherein the first sequence of thepayload segments includes all of the payload segments, and the secondsequence of the payload segments includes a subset of the payloadsegments.
 11. A tangible article of manufacture as defined in claim 9wherein the second sequence of the payload segments has a differentorder and a different number of payload segments than the first sequenceof the payload segments.
 12. A tangible article of manufacture asdefined in claim 8 wherein the machine readable instructions, whenexecuted, further cause the machine to: format the audience measurementdata into a plurality of payload segments containing the different typesof audience measurement data, the plurality of payload segmentsincluding a transport identifier segment, a major channel segment, aminor channel segment and a time segment, the audience measurement datafurther including a first index to represent an ordering of the payloadsegments and a second index to represent a number of payload segments tobe included in a particular frame of the compressed media data stream;vary the ordering of the payload segments inserted at the locations ofthe contiguous sequences of skip bytes in the two different frames ofthe compressed media data stream; and vary the number of the payloadsegments inserted at the locations of the contiguous sequences of skipbytes in the two different frames of the compressed media data streambased on the respective lengths of the contiguous sequences of skipbytes in the two different frames of the compressed media data stream.13. A tangible article of manufacture as defined in claim 8 wherein themachine readable instructions, when executed, further cause the machineto extract program and system information protocol data multiplexed withthe compressed media data stream to determine the audience measurementdata.
 14. A tangible article of manufacture as defined in claim 8wherein the machine readable instructions, when executed, further causethe machine to modify program and system information protocol datamultiplexed with the compressed media data stream based on the audiencemeasurement data inserted in the compressed media data stream.
 15. Anapparatus to insert audience measurement data in a compressed media datastream, the apparatus comprising: a data generator to format theaudience measurement data into payload segments corresponding to thedifferent types of audience measurement data; and a data insertion unitto: rearrange data in frames of a compressed media data stream to formcontiguous sequences of skip bytes at respective locations in the framesof the compressed media data stream, the audience measurement data to beinserted in the compressed media data stream at the locations of thecontiguous sequences of skip bytes, the contiguous sequences of skipbytes having respective lengths; and insert different payload segmentsof audience measurement data at the locations of the contiguoussequences of skip bytes in two different frames of the compressed mediadata stream based on the respective lengths of the contiguous sequencesof skip bytes in the two different frames of the compressed media datastream.
 16. An apparatus as defined in claim 15 wherein the datainsertion unit is to: insert a first sequence of the payload segments ina first frame of the compressed media data stream based on a length of afirst contiguous sequence of skip bytes in the first frame; and insert asecond sequence of the payload segments in a second frame of thecompressed media data stream based on a length of a second contiguoussequence of skip bytes in the second frame, the length of the secondcontiguous sequence of skip bytes being different from the length of thefirst contiguous sequence of skip bytes.
 17. An apparatus as defined inclaim 16 wherein the first sequence of the payload segments includes allof the payload segments, and the second sequence of the payload segmentsincludes a subset of the payload segments.
 18. An apparatus as definedin claim 16 wherein the second sequence of the payload segments has adifferent order and a different number of payload segments than thefirst sequence of the payload segments.
 19. An apparatus as defined inclaim 15 wherein the payload segments include a transport identifiersegment, a major channel segment, a minor channel segment and a timesegment, the audience measurement data further includes a first index torepresent an ordering of the payload segments and a second index torepresent a number of payload segments to be included in a particularframe of the compressed media data stream, and the data insertion unitis to: vary the ordering of the payload segments inserted at thelocations of the contiguous sequences of skip bytes in the two differentframes of the compressed media data stream; and vary the number of thepayload segments inserted at the locations of the contiguous sequencesof skip bytes in the two different frames of the compressed media datastream based on the respective lengths of the contiguous sequences ofskip bytes in the two different frames of the compressed media datastream.
 20. An apparatus as defined in claim 15 further comprising aprogram information modifier to modify program and system informationprotocol data multiplexed with the compressed media data stream based onthe audience measurement data inserted in the compressed media datastream.